Optical Nonlinearity of Violet Phosphorus and Applications in Fiber Laser

Violet phosphorus (VP) has attracted much attention due to its unique photoelectronic properties as a new two-dimensional nanomaterial, but its potential application in ultrafast photonics remains largely unexplored. In this paper, a D-shaped fiber is coated with VP to create a saturable absorber (SA), and its modulation depth is 3.68%. Subsequently, the SA is inserted into fiber laser, enabling successful generation of a dark soliton and bright-dark soliton pair through adjustment of the polarization state within the cavity. Through further study, mode-locked pulses are achieved and they are proved the existence of polarization-locked vector solitons. The results indicate that violet phosphorus can be used as polarization-independent saturable absorber.